The invention relates to an accelerator agent comprising a novel blend of aldehyde-amine condensation product and aliphatic amines, for use with diaminic, metal oxide, sulfur, and triazine crosslinkable elastomers, in particular, ethylene acrylate elastomers (AEM) and polyacrylate elastomers (ACM), polyisoprene (IR), styrene butadiene (SBR), acrylonitrile butadiene (NBR), ethylene-propylene diene terpolymers (EPDM), isobutylene-co-isoprene (IIR), chlorinated isobutylene-co-isoprene (CIIR), and brominated isobutylene-co-isoprene (BIIR).
Diaminically crosslinkable ethylene acrylate elastomers (AEM) and polyacrylate elastomers (ACM) are relatively inexpensive elastomeric materials which are of interest in the area of seals, particularly those used in various elements of vehicle engines. AEM elastomers are available, for example, from DuPont under the trade name Vamac®, while ACM elastomers are available from Zeon Chemicals, for example, under the trade names Nipol® and HyTemp®.
Those AEM and ACM elastomers which are accessible to diaminic crosslinking comprise so-called cure site monomer units whose content in the elastomer is normally approximately 1 to approximately 5 phr. Conventionally, diaminically crosslinkable AEM and ACM elastomers are crosslinked with crosslinking agents such as, for example, hexamethylene diamine carbamate, N,N-dicinnamylide diamine carbamate, 4,4-diaminodicyclohexylmethane, m-xylene diamine, 4,4-diaminodiphenylmethane, 4,4-diaminodiphenyl ether and 2,2-bis[4-(4-amino-phenoxy)phenyl]propane, which can be used individually or in mixtures. Other suitable diamine crosslinking agents belong to the group of hexamethylene diamines.
US 2009/0270549 teaches a crosslinking agent for diaminically crosslinkable ethylene acrylate (AEM) and polyacrylate (ACM) elastomers, comprising a diamine crosslinker, an accelerator selected from 1,8-diazabicyclo-5,4,0-undec-7-ene (DBU), derivatives and salts thereof, and a moderator of the pyrrolidone type. The reference notes that while DBU, a tertiary amine, was a known accelerator, it was not possible to use with these AEM and ACM elastomers as it resulted in inferior compression set at elevated temperatures. The reference teaches that the problem is overcome by combining DBU with a moderator.
Polychloroprene (CR) and natural rubber (NR) elastomers are relatively inexpensive elastomeric materials which are used in many broad range rubber applications. CR elastomers are available, for example, from DuPont under the name Neoprene, while NR elastomers are widely available under many technical specified descriptions of natural rubber.
General purpose CR is used in molded and extruded goods, hoses, belts, wire and cables, heels and soles of shoes, coated fabrics, and gaskets. Most natural rubber is used in tires and automotive products. Other major applications of NR are industrial and engineering goods, footwear and adhesives.
CR and NR use differing crosslinking systems for their different polymeric chemical makeup. CR uses metal oxides as a curative while NR uses sulfur as its curative. Both crosslinking systems are used together with an accelerator, of which can be from a wide variety of chemical groups.
Polyepichlorohydrin is a triazine crosslinkable elastomer group, of which epichlorohydrin polymer (CO), copolymer of epichlorohydrin (ECO), and terpolymer of epichlorohydrin (GECO) are examples. Polyepichlorohydrin elastomers have a balance of properties that make it useful in automotive seals and hoses, and are available from Zeon Chemicals, for example, under the trade name Hydrin®.
Triazine crosslinking systems can be used with a variety of accelerators and retarders to make the cure systems widely adjustable.
These crosslinking systems are used together with an accelerator, which is preferably taken from substances of the guanidine group, to which, in particular, the accelerators OTBG, DOTG, DPG and/or biguanidine belong. However, due to possible toxicological problems, it is likely that these systems, particularly DOTG, will be phased out under regulatory requirements.